In the process of producing a semiconductor device such as IC and LSI, fine processing by lithography using a photoresist composition has been conventionally performed. Recently, with increase in the integration degree of an integrated circuit, formation of an ultrafine pattern in the sub-micron or quarter-micron region is being required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to l line or further to KrF excimer laser light.
At present, other than the excimer laser light, development of lithography using electron beam, X ray or EUV light is proceeding. Above all, the lithography using EUV light as a light source is positioned as a next-generation or next-next-generation promising pattern formation technique, and studies thereon are being aggressively made. The performances required of the resist used are high sensitivity, high resolution and good line edge roughness. However, these performances are in a trade-off relationship and it is important how to satisfy these performances at the same time. The line edge roughness as used herein means that the resist edge at the interface between the resist pattern and the substrate irregularly fluctuates in the direction perpendicular to the line direction due to the resist property and when the pattern is viewed from right above, the edge gives an uneven appearance. This unevenness is transferred by the etching step using the resist as a mask and causes deterioration of electric property, resulting in decrease in the yield, Particularly, in an ultrafine region of 0.25 μm or less, the improvement of line edge roughness is an essential problem to be solved. Such a problem is also important in the lithography using X-ray or electron beam.
As for the resist suitable for the lithography process using electron beam, X-ray or EUV light, a chemical amplification-type resist utilizing an acid catalytic reaction is mainly used from the standpoint of elevating the sensitivity and in conventional resists, there has been studied a chemical amplification-type resist composition mainly comprising an acid generator and a phenolic polymer which is insoluble or sparingly soluble in an aqueous alkali solution but becomes soluble in an aqueous alkali solution under the action of an acid. However, the conventional photoresist using a polymer compound for the substrate has a problem that the molecular shape of the polymer compound is reflected on the pattern profile or line edge roughness.
On the other hand, in the light of fine pattern formation and low line edge roughness, a low molecular material is recently attracting attention. In particular, a molecular resist using a simple molecule as the binder has been proposed, and there have been disclosed resist compositions using, for example, a phenol-based compound derivative having a specific structure (see, for example, JP-A-2003-183227 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-10-120610), a calixarene having a specific structure (see, for example, JP-A-10-120610 and JP-A-11-322656), a calixresorciarene (see, for example, JP-A-11-322656 and JP-A-2003-321423), or a phenol-based dendrimer with the mother nucleus being a calixresorcinarene (see, for example, JP-A-10-310545). A resist composition using a polyvalent phenol compound (JP-A-2005-266740) has been also disclosed.
However, it is pointed out that when such a molecular material is merely used, significant pattern falling occurs in the ultrafine region. An effective measure for solving this problem has not yet been found out.